Ultraviolet and infrared light decontamination and the secondary pollution products of G-series nerve agent simulant model molecules contaminating TiO2/Ti surfaces

Abstract

• Photo-decontaminations of G-series nerve agent simulant model molecules were tested under scanning 266-nm laser, UVA/UVB/UVC, and IR. • Photodecomposition products and the reaction pathways were discussed on the basis of GC, Mass, XPS, EDXS, and FT-IR. • Cleavages of P−CH 3 , P H, P O, C–H, PO−CH 2 CH 3 , and POCH 2 −CH 3 bonds of DMMP, DMP, DEMP, and DEP were fully discussed. • Dissociative adsorption and photocatalytic dissociation were discussed with active species of O 2 ― , h + and •OH. • MeOH and EtOH were major products dependent on light exposure, wavelength, photon flux, and the chemical groups. Ultraviolet (UV) photodecontamination of chemical warfare agents (CWAs) has been an attractive way for decontamination of target areas unapproachable by a wet chemical method. Herein, decontamination was demonstrated using UV and infrared lamps and a home-built scanning 266-nm pulse laser under air and N 2 conditions for the G-series nerve agent simulant model molecules of dimethyl methylphosphonate, dimethyl phosphite, diethyl methylphosphonate, and diethyl phosphite contaminating TiO 2 /Ti sheets. Volatile secondary photodecomposition products were examined by gas chromatography and mass spectrometry, and nonvolatile surface residues by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction crystallography, and Fourier-transform infrared spectroscopy. The wavelength- and power-dependent mechanisms of the formation of diverse secondary products, the role of active O 2 − , h + and •OH species, and the mechanisms of dissociative adsorption and photodecontamination were fully discussed and found valuable for the development of a remote laser photodecontamination method applicable to diverse CWA-contaminated target areas.